> 2.- =BFDoes amanda allways rewinds the tape before writing to it (so =
> tape is
> allways overwrited)? (I think this is true)

Yes for sure.

>  3.- On the other hand, incremental, AFAIK, means "backup of all the =
> files
> that have changed since the last backup, even if that was an incremental
> backup (as opossed to a full backup)". Is there a way to make a =
> differential
> backup ("backup of all the files that have since the last FULL backup").

Incremental always come with a level, full backup having the level 0.

Incremental of level X means "all the files that have changed since
the last backup of level less than X":

level 1 means all the files that changed since the last level 0 (full)
level 2 means all the files that changed since the last level 0 or 1
level 3 means all the files that changed since the last level 0 or 1 or 2

> "backup of all the files that have since the last FULL backup"

Is exactely incremental level 1.

Olivier